In recent years, with advance of information communication technologies, a technology regarding augmented reality, in which visual information is added to an image obtained by imaging a real environment (outside) by using a computer has been developed. For display of the visual information, a wearable device such as an HMD (head mounted display) equipped with a camera for obtaining an outside image is mainly used to display detailed information regarding an object present in a direction of a field of view of a user (hereinafter referred to auxiliary information) as being superposed on the outside image. The auxiliary information includes information obtained from the outer appearance of the object, as well as information not appearing from the outer appearance of the object, such as an environment where the object was manufactured and information about reputations about the object from other users.
Here, when the user selectively obtains any one piece of auxiliary information from among a plurality of pieces of auxiliary information, an operation of an input device from the user is performed. In an example of the input device, a conventional input device may be used such as a mouse or keyboard. As a simple and efficient input method, a method of using a movement (a gesture) of the user as an input tool has attracted attention. An example of technology in which a user movement is used as an input tool is disclosed in Japanese Laid-open Patent Publication No. 10-214346 in which an acceleration sensor is used to determine a movement of fingers of the hands. Also, Japanese Laid-open Patent Publication No. 2011-14082 discloses a technology of determining a movement of a visual line by a visual line detecting device mounted with a wearable device.
Also, a method of using a movement of the head (including the neck) allowing hands-free or eyes-free recognition of a user movement has also attracted attention. In a recognizing method by a movement of the head, a user movement that reflects the intentions in actual human daily movements such as nodding or rejection may be used.
As an example of the method of using a movement of the head, Haiyuan Wu, et. al., “Head Gesture Recognition from Time-Varying Color Images”, Journal of Information Processing, 40(2), pp. 577-584, 1999 discloses a technology in which a movement of the head is determined by finding the location of the head from a sensor placed outside. Also, Japanese Laid-open Patent Publication No. 2006-243784 discloses a technology in which a movement of the head is determined by analyzing a value obtained from an acceleration sensor mounted with the head of the user.